Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Deferred Income	$ 107,000,000				$ 104,000,000
Loans modified in TDRs	10,588,000				7,151,000
Unfunded commitments available for funding	3,100,000
Loans modified in TDRs during the period	5,280,000	[1]	12,133,000	[1]
Payment Deferrals Granted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans modified in TDRs during the period			$ 9,300,000

[1] There were no partial charge-offs on loans classified as TDRs during the three months ended March 31, 2015 or March 31, 2014.